Unfortunately, your Pediatrician is correct -- there's really nothing you can do. But on the positive side, there's nothing going "wrong" with your child either...and he won't have any memory of the event.
The difference between a night terror and a nightmare is that a Night Terror only happens during non-REM (Rapid Eye Movement) sleep. We do not dream during non-REM sleep (it's our "deep sleep"), so a child having a night terror is NOT dreaming. Research indicates that Night Terrors happen during the first third to half of the night, when the majority of non-REM sleep is occurring.
Since he is not dreaming during a Night Terror, there will be no memory of the event from the child -- he is in deep sleep. The only person who is scared during the Night Terror is the person/people watching the child have the event!
Even though it is very unnerving to see your child in such a bizarre state, there is nothing dangerous about Night Terrors and there is nothing you can do about it (except make sure that your child doesn't accidentally hurt himself by falling down the stairs or things like that). I was told to NOT try to wake the child. Just let the event end on it's own and your son will go back to sleep.
I hope this helps in some way. Don't be overly frightened. We went ahead and picked-up our daughter and held her. However...it didn't make a difference for her. The Terror continued until it was done.